Cobalt

Agent Name
Cobalt
CAS Number
7440-48-4
Formula
Co
Major Category
Metals
Synonyms
Cobalt metal dust; Cobalt metal fume; [NIOSH]
Category
Elements, Metallic
Description
Odorless, silver-gray to black solid; [NIOSH]
Sources/Uses
Occupational asthma reported in hard metal grinders and diamond polishers; [Malo] Allergic contact dermatitis in electronics workers; [Marks] Cobalt skin allergy often accompanies chromium and nickel sensitization. Cobalt skin allergy affects workers in several industries (hard-metal, construction, electronics, dental alloys, cement, pottery, glass, electroplating, and batteries). [Kanerva, p. 505] Also used in orthopedic prostheses, glass and paint pigments, and catalysts; it may be released in emissions from burning fossil fuels. Cobalt is an essential nutrient in the human diet in the form of Vitamin B12 (cyanocobalamin). Radioactive cobalt is used in medicine and food/equipment irradiation. [ATSDR ToxProfiles] In industry, mainly used to make alloys and hard metal (powder preparation, pressing, and shaping); Hard metals contain tungsten carbide (90%) and cobalt metal (10%); CoCrMo (Vittalium) is an alloy used in joint replacements; May be added to fertilizers for low-cobalt soils; [Nordberg, p. 743-5] Cobalt oxides (may refer to CoO, Co2O3, and Co3O4) used in ceramic and enamel pigments, oil refining, batteries, cobalt refining, digital video cassettes, tool & die materials, and animal nutrition; [ACGIH]
Comments
Cobalt is rapidly excreted in the urine; It may accumulate in the lung after inhalation of insoluble compounds; Goiter is a known side effect of cobalt treatment for anemia; Hard metal lung disease is caused by the composite material, a mixture of cobalt and tungsten carbide, that can injure the lung by producing toxic oxygen species; Also may occur after exposure to cobalt metal powder mixed with iron and diamond dust in diamond polishers; There is no evidence that cobalt metal alone or other cobalt compounds can cause hard metal disease; [Nordberg, p. 753] Pulmonary edema can result from heavy exposure to cobalt fumes. [Harber, p. 496] A cross-sectional study of 82 workers in a cobalt refinery with an average exposure of 8 years found mild thyroid dysfunction (decreased T3, T4, and increased TSH). No evidence of pulmonary fibrosis was found in these workers exposed to cobalt alone (not to hard metal). [Reference #1] An epidemic of cardiomyopathy occurred in the 1960s among heavy drinkers of beer containing cobalt. A recent study of cobalt workers correlated cumulative cobalt exposure with echocardiographic changes but not with cardiac dysfunction. [Reference #2] Cobalt is a "hepatotoxic agent." [Zimmerman, p. 4] Can cause occupational contact urticaria; [Kanerva, p. 219] "Accordingly, a TLV-TWA of 0.02 mg/m3, as Co, is recommended to minimize the potential risk of developing asthma, pulmonary function changes, and myocardial effects. The recommended TLV applies to elemental cobalt and inorganic compounds, but not to cobalt exposure in the cemented tungsten carbide industry." [ACGIH] See "Effects of occupational cobalt exposure on the heart in the production of cobalt and cobalt compounds: a 6-year follow-up." [PMID 31745627] See "Tungsten carbide (cemented)." See "Cobalt-60" the most important radionuclide.
Biomedical References

Exposure Assessment

BEI
Cobalt in urine = 15 ug/L; sample at end of shift at end of workweek; See "Tungsten carbide (cemented)."
Skin Designation (ACGIH)
Insufficient data
Bioaccumulates
Yes
TLV (ACGIH)
0.02 mg/m3, as cobalt, inhalable particulate matter
PEL (OSHA)
0.1 mg/m3, as Co (metal dust and fume)
IDLH (NIOSH)
20 mg/m3
Excerpts from Documentation for IDLHs
It has been reported that animals chronically exposed for 3 years to a cobalt-metal blend at a concentration of 20 mg Co/m3 developed fibrotic lesions in the lungs [Patty 1963].
Explanatory Notes
Cobalt with tungsten carbide is classified as 2A (probably carcinogenic to humans). [IARC]
Half Life
Whole body (depends on compound and route): 5 days to 4 years; [TDR, p. 379]

Adverse Effects

Skin Sensitizer
Yes
Asthma
Yes
Toxic Pneumonitis
Yes
Fibrogenic
Yes
Hepatotoxin
Hepatoxic (a) from occupational exposure (secondary effect) or (b) in animal studies or in humans after ingestion
IARC Carcinogen
Possible (2b)
NTP Carcinogen
Anticipated human carcinogen
ACGIH Carcinogen
Confirmed Animal

Diseases, Processes, and Activities Linked to This Agent

Diseases

Occupational diseases associated with exposure to this agent:

Activities

Activities with risk of exposure: